In moving tissues, undergoing complex motion patterns, it is often challenging to visualize relatively small contrasts in X-ray fluoroscopy images. The situation can arise during imaging in embolization procedures where an embolization agent is deposited at a region of interest inside a patient.
A more specific example is a liver intervention, where the motions of the ribcage, heart, diaphragm and/or bowels combine to cause examples of such complex motion patterns. An additional factor that makes X-ray imaging challenging is that the transparency images created in X-ray usually feature several superimposed motion layers.
Sometimes subtraction imaging techniques are used to enhance the (image) contrast visibility but motions remain still a concern. A common subtraction based technique that uses contrast agents for visualizing is called DSA (Digital Subtraction Angiography). A refined example of this technique developed for cardiac interventions can be found in U.S. Pat. No. 4,729,379.
However, due to the very low contrast of the embolization material, the presence of in particular non-rigid movements of the tissue in embolization interventions (in particular, but not only, abdominal embolization) and the abundance of background tissue, visualization remains a challenge and known DSA techniques appear not to yield satisfactory imaging results.